CTB 6 – Molecular regulation of developmental processes

Question 1

What is the difference between the development of early or late defects with respect to craniofacial malformations?

Answer 1

Early developmental defects cause severe craniofacial malformations which are lethal, but later are less severe which allow survival

Question 2

What is holoprosencephaly?

Answer 2

Insufficient division of the cerebral hemispheres

Question 3

What is anencephaly?

Answer 3

Spina bifida

Question 4

How is anencephaly prevented?

Answer 4

Folic acid

Question 5

What is the main symptom in agnathia?

Answer 5

Mandible not present

Question 6

What is the mildest form of cleft lip?

Answer 6

Cleft uvula

Question 7

What is the most severe form of cleft lip?

Answer 7

Bilateral cleft lip and palate

Question 8

What is ectodermal dysplasia?

Answer 8

Malformation of teeth

Question 9

What is the main gene involved in the spectrum of facial midline disorders, ranging from holoprosencephaly and frontonasal dysplasia? How does the gene signal in these diseases?

Answer 9

SHH

Loss of SHH cell signalling in holoprosencephaly

Overactivation of SHH cell signalling in frontonasal dysplasia

Question 10

What genetic factors can cause impaired early embryonic developmental processes?

Answer 10

Mutations in development genes, chromosomal abnormalities, abnormal gene regulation

Question 11

What environmental factors can cause impaired early embryonic developmental processes?

Answer 11

Alcohol, smoking, drugs, etc….

Question 12

What is gastrulation?

Answer 12

3 layers (ectoderm, mesoderm, endoderm) develop and fold to form a more complex organism

Question 13

What derivative in the ectoderm forms craniofacial tissues?

Answer 13

Neural crest

Question 14

What is organogenesis?

Answer 14

How body plan is established

Question 15

What are the 4 types of cell communication?

Answer 15

Endocrine
Paracrine
Neuronal
Contact-dependent

Question 16

What happens to a cell if it isn’t programmed to signal?

Answer 16

Cell dies

Question 17

What is the function of the phosphorylation cascade in cell signalling?

Answer 17

Induced by extracellular signal molecules to give out different cell responses

Question 18

What do signalling molecules induce?

Answer 18

Transcription factors

Question 19

What do transcription factors regulate?

Answer 19

Signalling molecules

Question 20

Name signalling molecules.

Answer 20

Fgf - fibroblast growth factors
Tgfß - transforming growth factor ß
Bmp - bone morphogenic proteins
Hh - hedgehog

Question 21

Name transcription factors.

Answer 21

Hox - homeobox
Msx - muscle segment homeobox
Dlx - distal-less homeobox
Barx - barH-like homeobox
Pax - paired box

Question 22

What is the function of morphogenic gradients integrated at cellular level?

Answer 22

Regulate morphogenesis

Question 23

What are denticles?

Answer 23

Tooth-like projections

Question 24

Where is the opposing gradients of signalling molecules within the neural crest?

Answer 24

Neuroectoderm and epidermis

Question 25

What are the genes in the opposing gradients of signalling molecules within the neural crest?

Answer 25

Overlapping gradients of BMP4 and WNT6 signalling proteins

Question 26

What do the genes in the opposing gradients of signalling molecules within the neural crest induce expression of?

Answer 26

FoxD3 and slug | TF needed for cell specification and migration

Question 27

What protein does the Hox gene encode?

Answer 27

DNA-binding homeodomain

Question 28

What does Pax9 cause?

Answer 28

Oligodontia - more than 6 teeth missing

Question 29

What does Pax3 cause?

Answer 29

Waardenburg syndrome

Question 30

Where is Pax3 expressed?

Answer 30

Neural crest, muscle and CNS

Question 31

What are the symptoms of Waardenburg syndrome?

Answer 31

- White hair colour - Wide-spaced eyes (hypertenlorism) - Short, broad nose - Epicanthal folds

Question 32

What are epicanthal folds?

Answer 32

Fold of the upper eyelid covering the inner corner of the eye

Question 33

What basic mechanism regulates organogenesis?

Answer 33

Reciprocal epithelial/mescenhymal interactions

Question 34

Within tooth development what happens in the initiation stage?

Answer 34

- Overlapping gradients of signalling molecules, FGF and BMP in the dental epithelium - Induce transcriptional response, PAX9 and MSX1 in the dental mesenchyme - Determines tooth position

Question 35

Within tooth development what happens in the bud stage?

Answer 35

- Dental mesenchyme secretes signalling molecules | - Induces formation of the enamel knot (non-dividing cells) in the dental epithelium

Question 36

Within tooth development what happens in the cap stage?

Answer 36

- Enamel knot secretes signalling molecules that induces cell cycle arrest (BMP) within enamel knot cells, but induces cell proliferation (FGF) in surrounding cells - Determination of tooth shape